Electrical condenser



March 31, 1942. w, GODSEY' JR 2,277,968

- ELECTRICAL CONDENSER Filed July 16, 1940 2 Sheets-Sheet 1 17 25 57 1o 14 as w 1 x I l k 11111111111 I I! l I 2 F hfi FL I m 23 y LJJ u u 21 llllllllllllmfllllllllllHIHIHIIIIIIIIIIIII Illl 19 12 25 27 219 11 2515 17 14 15 15 1a 29 2o 52 Pal.

23 ll llll II I 39 19 3a 35 12 35 36 3a 2b FRANK W GOOSE), JR. INVENTOR.

ATTORNEYS.

March 31, 1942. w, o s JR 2,277,968

ELECTRICAL CONDENSER Filed July 16, 1940 2 Sheets-Sheet 2 10 \W K I l 2.9 29

FRANK M 60085), JR. 1N VENTOR.

ATTORNEYS.

Patented Mar. 31, 1942 2,277,968 suic'rnio'u. cosnsusna Frank w. Godsey, In, strut Adams, as-

signor to Sprague Specialties 00., North Adams, Mast, a co poration of Massachusetts Application July 16, 1940, Serial No. 345,831

'lCiaims.

The present invention relates to variable condensers and more particularly to a new and novel condenser tuning assembly embodying condensers of the type described inthe copending application of Robert C. Sprague and Frank W. Godsey, Jr., Ser. No. 336,822, filed May 23, 1940.

Condensers described in said application comprise as their main elements two closely spaced concentric conducting cylinders which serve as the two electrodes of the condenser and which are displaceable relative to each other to vary the capacity of the condenser. Interposed between the electrodes is a dielectric layer which preferably consists of a vitreous material forming a fused integral coating on. the surface of the inner electrode. Preferably, the electrodes and the coating are made to close tolerances in their coacting dimensions as to engage each' other with a smoothly sliding fit.

Tuning condensers of this type have many advantages, as they combine a wide capacity range and great mechanical and electrical stability throughout their capacity range with a small size and a compact and light weight structure which can be manufactured at low cost.

Such tuning condensers possess inherently a linear capacity-stroke characteristic, ,but by means of suitable mechanical driving means the relationship between the capacity of the condenser and the displacement (or rotation) of the I tuning control can be made of any other desired important'requirements. It must be such that without the need of absolute parallelism of the axes of the individual condensers and of a close tolerance positioning of the condensers within the assembly, no binding between the components of the condensers takes place. At the same time the assembly must be such that the corresponding electrodes of the individual condensers are immovable relative to each other which movement would preclude an accurate "tracking" of the condensers throughout their tuning range. a I

A further requirement of such an assembly is that it readily lend itself to diverse driving means for simultaneously varying the capacity of all the condenser units whereby any desired relationship between the capacity of the condensers and the displacement (or rotation) of the tuning control can be effected.

It is an object of the invention to provide a novel tuning condenser assembly comprising ganged condensers oi the above described type.

in'which assembly the full inherent advantages dividual condensers within the assembly.

Another object of the invention is to provide a tuning condenser assembly ,which readily lends itself to various types of driving means for simultaneously varying the capacity of the condensers of the assembly.

' will be described with reference to the appended drawings forming part of the specification and in which;

Figure 1 is a plan view partly in section illustrating the condenser assembly of the invention. Fig. 2 is a side-view in section taken along the line 2-2 of Fig. 1.

Fig. 3 is an end view in section taken along the line 3-4 of Fig. 2. Fig. 4 is a side view in section similar to Fig. 2 and illustrates the assembly of the invention provided with a self-contained driving mechanism for simultaneously varying the capacity of the individual condensers. V

Referring to Figs. 1 to 3,-the condenser assembly there shown comprises two condenser units ill and H mounted in a manner later to be more fully described, on a base 12 consisting preferably of a sheet of hard metal, for example, of 'cold rolled steel. The base I! is provided with tapped holes 38-" adapted to receive suitable bolts (not shown) for mounting the tuning assembly.

Condensers Ill and II are of identical construction and each comprises as one electrode, a metal cylinder is and as the second electrode, a hollow metal cylinder or sleeve ll concentrlcal ly surrounding the electrode I I. Electrodes I3 and H are displaceable relative to each other to vary the capacity of the condenser.

Interposed between the electrodes is a dielec-- tric layer ll forming an integral fused coating on the surface of electrode It. The dielectric layer l5 consists preierably of a potassium-lead silicate vitreous enamel as disclosed in the copending application of Stanley 0. Dorst, Ser. No. 289,292, filed August 9, 1939. The layer i5 may consist of other suitable dielectric materials, for example, of various kinds of vitreous enamels, or of non-vitreous dielectric materials such as cellulose acetate, polystyrene, hard rubber or the like, to which d electric materials may be added a filler of titanium dioxide or other dielectric material to increase the dielectric constant and/or lower the power factor.

The layer I5 is applied to the electrode l3 preferably by the cataphoretic deposition process described in the copending application of Preston Robinson et al., Ser. No. 197,692, filed March 23, 1938, which process produces a coating of high uniformity and of even thickness throughout the length of the coating. As a rule, the so-deposited coating is fused and thereafter subjected to surface grinding as described in the above-referred to copending application of Robert C. Sprague et al. whereby the coated electrode |3i5 engages the sleeve electrode ll with a smoothly sliding lit and an air layer or gap I6 having an average thickness of the order of .00025" to .0005" is formed between these elements.

For the guiding of the sleeve electrode H in its movement relative to the coated electrode "-45, there is provided a guide abutting against the closed end of electrode l3i5 and consisting of a low-loss insulating material such as Bakelite," hard rubber, "Isolantite or the like. Guide 2| is preferably hollow throughout its length except for the portion 26 abutting against the electrode "-45. At their adjacent ends the electrode li-ll and the guide 25 are provided with axial bores through which passes a spindle bolt l1 securing these members together by means of an integral shoulder III which abuts against the closed end of the electrode and a nut 21 which abuts against the portion 26 of the guide. A look washer 2| is interposed between the nut 21 and the portion 26 to prevent loosening of nut 21 by vibration or other mechanical shock.

Each condenser is supported within the assembly by means of its spindle bolt l1 and two mounting strips l9 and 20 through suitable bores of which the projecting ends of bolt I? pass as a snug fit. Strips l9 and 20 consist of an insulating material, for example, of hard rubber, "Bakelite" or the like, and are secured to the base l2 by rivets 23 and 24 respectively, passing through these members and mounting brackets 2I22 consisting of extending portions of the base l2.

To secure the bolt II within the mounting strips l9 and 20, the bolt is provided at its portion entering the strip 20, with a formed nut 28 consisting of a U shaped resilient metal strip straddling the mounting strip 20 and one arm 30 of which is threaded to receive the spindle bolt I1. Preferably, the strip 20 is notched at 40 to receive the nut 29.

For the outside electrical connection to each electrode "-45 there is provided a terminal lug 22 consisting of an integral extending portion of the nut 29.

Tuning of the condenser assembly takes place by the simultaneous displacement oi the sleeve electrodes l4 relative to the coated electrodes lt-IS. For this purpose the sleeve electrodes are ganged together by a resilient metal yoke member which in accordance with the invention, on one hand permits unrestricted radial or transverse movement of the sleeves il-ll relative to each other and on the other hand prevents lateral movement of the sleeves relative to each other.

The use of such a yoke member obviates the requirement of a close tolerance positioning of the condenser units within the assembly. Furthermore, by the use of such a yoke member the necessity of absolute parallelism between the axes of the coated electrodes it obviated, and the sleeve electrodes align themselves with the coated electrodes, thereby precluding any possibility of binding between these members throughout the entire movement of the sleeves.

While the sleeve electrodes are permitted substantially unrestricted radial or transverse movement relative to each other, they are at the same time precluded from any lateral movement relative to each other whereby no lost motion exists between'these members and any preset "tracking" of the condensers of the assembly is maintained throughout theadjustment range of the condensers.

A yoke capable oi so functioning is shown in Figs. 1 to 3 as 23 and comprises a substantially channel-shaped flexible metal strip, for example, of phosphor bronze, having a central portion N, and side walls 35-45 each of which side walls extend into mounting arms 3H6 disposed substantially at right angles to the side walls. The arms 38 carry the sleeve electrodes I l-ll to which they are secured by soldering, welding or the like.

'I-he condensers of the assembly are simultaneously adjusted by the lateral movement of the yoke 32 causing a corresponding movement of the sleeve electrodes i4 relative to the coated electrodes li-IS. For this purpose, the central portion 34 of the yoke is formed with two punched out ears 21-41 to which the two ends oi a dial cord (not shown) are attached in known manner. Electrical connection to the sleeve electrodes 14- is provided through the yoke 33 which is maintained at ground potential by a suitable connection, for example, by the dial cord itself which consists preferably of a flexible wire or braid of bronze or the like.

Besides being simultaneously adjustable, the condensers of'the assembly are also independently adjustable, whereby the capacities thereof can be either equalized or made to assume a constant difference throughout the adjustment range of the condensers. This is achieved by the lateral movement of the coated electrode l3-i5 relative to the sleeve electrode II by turning the spindle bolt II, for example, by means of a screw driver engaging its slotted end 29.

While in Figs. 1 to 3 a tuning assembly comprising only two condenser units is illustrated, it should be well understood that the invention is equally applicable to a tuning assembly comprising morethan two condenser units, in which assembly each pair of adjacently disposed sleeves H are ganged together by a yoke 33 which permits unrestricted radial or transverse movement of the sleeve electrodes relative to each other, but which yoke restricts lateral movement of these elements relative to each other.

In Fig. 4 there is shown the tuning assembly of the invention provided with a driving mechanism for the simultaneous adjustment of the individual condensers, which driving mechanism is wholly contained within the tuning assembly.

While in the tuning assembly of Fig, 4 only one condenser unit is shown, it should be well understood that the following description applies The individual condensers making up the assembly of Fig. 4 are identical to those shown in Figs. l'to 3 and the individual elements of the condensers need not again be described.

The assembly shown in Fig. 4 comprises individual condenser units It secured to a mounting base Ii consisting of a sheet of hard metal and comprising integral brackets I! and I3 and tapped mounting holes "-51. Each condenser comprises an inner cylindrical electrode I4, an outer concentric electrode II and a dielectric layer It forming an integral coating on the inner electrode 84. Abutting against the closed end of electrode 54 is a guide cylinder It. The electrodes N and I, the dielectric layer BI, and the guide 58, conform to the corresponding elements previously described in connection with Figs. 1 to 3.

Thelead screw H is supported within the tuning assembly by means of the brackets I! and II through suitable bores of which members pass the ends of the lead screw preferably with a close bearing fit. The unthreaded end of lead screw ll protruding beyond the strip I is provided with a shaft II for receiving a suitable tuning knob (not shown), the lead screw being secured .within the shaft I! as by a forced fit.

The lead screw is locked within the assembly by means of a split locking collar II which engages an annular slot in the unthreaded portion of the lead screw and abuts against the strip I.

To prevent its lateral movement, the lead screw II is provided with a helical spring '0 surroundingits protruding portion which spring abuts with its ends against the end face of the shaft II and the mounting flange It.

In Fig. 4 a lead screw ll having a uniiorm pitch is illustrated whereby the capacity the condensers varies linearly with rotation of the Each condenser is supported within the assembly by a spindle bolt is and two insulating mounting strips Cl and II through suitable bores oi which pass the ends of the bolt It. The mounting strips CHI are secured to the base It by rivets l2 and 08 respectively, passing through the mounting strips and the mounting brackets l2 and I3.

To position the bolt I! relative to the mounting strips 60-", it is provided with a formed nut 64 consisting of a suitably shaped metal strip straddling the mounting strip II. The nut 04 also extends into a terminal tab it for the external electrical connection to the coated electrode 54-".

Each of the condensers is independently adjustable by the lateral movement of its coated electrode H8 relative to the sleeve electrode 50 by threading or unthreading-the spindle bolt 89 through the nut 84 and the mounting strips Cl and II.

For the simultaneous adjustment or the condensers the outer sleeve electrodes Bl are ganged together by a yoke 68 which in accordance with the invention permits unrestricted radial or transverse movement of the sleeve electrodes relative to each other and which at the same time prevents lateral movement of the sleeve electrodes relative to each other. the yoke 33 of Figs. 1 to .3 and comprises a substantially channel-shaped resilient metal strip having a central portion 01 and side walls 0! each of which side walls extend into substantially perpendicularly disposedmounting arms "-4! to which the sleeve electrodes II are secured by soldering, welding or the like. While the yoke 80 of Fig. 4 is shown to be identical to the yoke 33 of Figs. 1 to 3, it should be well understood that the invention includes yokes 01' other shapes which permit unrestricted radial or transverse movement of the sleeve electrodes relative to each other and which preclude lateral movement of the sleeves relative to each other.

For'the lateral movement of the yoke it and the simultaneous adjustment of the capacity of the condensers there is provided a driving mechanism consisting of a travelling nut 10 aiilxed to theyoke 60 and a lead screw H. As shown the nut 10 comprises a channel'shaped rigid metal strip comprising a central portion 12 secured to the yoke 68 by rivets Ii-II, an arm 14 having a threaded bore 16 engaging the threads of the lead screw H, and an arm," with a bore 11 for guiding the nut 10 on the lead screw.

The yoke 08 is similar-to I control shaft ll, however, it is to be noted that other relationships between capacity of the condensers and the rotation of the shalt can be readily. achieved. For example, where a straight line frequency characteristic is desired, this is achieved by the use of a lead screw Ii the threads of which have a imii'ormly varying pitch.

While I have described my invention by means of specific examples and in specific embodiments, I do not wish to be limited thereto for obvious modifications will occur to thoseskilled in the art without departing from the spirit and scope oi. the invention.

' What I claim is:

1. An adjustable condenser assembly comprising a mounting base and two condenser units disposed on said base, each oi said units comprising two concentric cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between the electrodes and forming an integral concentric coating on one electrode, insulating mounting strips secured to two opposing ends of said base, athreaded member engaging the inner electrode and threadbe independently laterally moved relative to the outer electrodes to independently adjust the pacity oi each condenser.

2. An adjustable condenser assembly comprising a mounting base and two condenser units disposed on said base, each of said condensers comprising two concentric cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between the electrodes and forming an integral concentric coating on the surface 01' one electrode, the inner *electrode of each condenser rigidly secured to said mounting base. a resilient channel member with ofi'set arm portions interposed between the outer electrodes oi said condensers, said electrodes secured to the arms 01' said channel member, means to simultaneously vary the capacity of said condensers, said means comprising a driving member adapted to laterally move said channel member.

3. An adjustable condenser assembly comprising a mounting base and two condenser units disposed on said base, each of said condensers comprising two concentric cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between the electrodes and forming an integral concentric coating on the surface of one electrode, the inner electrode of each condenser rigidly secured to said mounting base, a resilient channel member with oliset arm portions interposed between the outer electrodes of said condensers, said electrodes secured to the arms of said channel member. means tosimultaneously vary the capacity of said condensers, said means comprising a lead screw disposed within the tuning assembly and engaging said channel member.

4. An adjustable condenser assembly comprising a base and two adjacently disposed condenser units on said base, each of said condensers comprising two concentric cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between said electrodes and forming an integral concentric coating on the surface of one of said electrodes, an insulating mounting strip disposed on said base, a threaded member secured to the inner electrode of each condenser and securing same to said insulating strip, a resilient channel shape member securing together the outer electrodes of said condensers, said channel member permitting transverse movement of the outer electrodes and precluding lateral movement thereof relative to each other, means engaging said channel member to simultaneously vary the capacity of said condensers, the inner electrodes of said condensers independently adjustable relative to the outer electrodes by said threaded members.

5. An adJustable condenser assembly comprising a base and a plurality of adjacently disposed condenser units on said base, each of said units comprising two concentric cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between said electrodes and forming an integral concentric coating on the surface of one of said electrodes, mounting strips disposed at two opposing ends of said base, the inner electrode of each condenser rigidly secured to said mounting strips, a member interposed between each pair of adiacently disposed outer electrodes and securing together said outer electrodes, said member permitting transverse movement of the outer electrodes and precluding lateral movement thereof relative to each other.

6. An adjustable condenser assembly compris ing a mounting base and two condenser units on said base, each of said units comprising two concentric electrodes and a dielectric layer interposed between the electrodes, the inner electrode of each condenser secured to said base, a member securing together the outer electrodes of the condensers, said member being transversely flexible and permitting transverse movement of the outer electrodes relative to each other and being laterally rigid and precluding lateral movement of the outer electrodes relative to each other.

7. An adjustable condenser assembly comprising a mounting base and two condenser units on said base, each condenser comprising two cylindrical electrodes adapted to be laterally moved relative to each other and a dielectric layer interposed between the electrodes, the inner electrode of each condenser secured to the mounting base and the outer electrodes secured together by a member which is substantially rigid along an axis parallel to the longitudinal axis of the condensers and is substantially flexible along an axis perpendicular to the longitudinal axis of the condensers.

FRANK W. GODSEY, Ja. 

